I'm researching the ballast tank system on Type VIIs to see how we will fit it in the game.

The Type VII had many tanks, including trim tanks, torpedo compensating tanks, MBT 1,2,3,4, & 5, regulatory tanks, and a pair? of negative tanks. I say pair, because they apparently wrap around the bottom of the sub? so you have a port and stbd pair of tanks for MBT 2, 4 and the negative tank that are connected beneath the boat?

The MBT 1, 3, and 5 seem to be a set of single tanks on the centerline of the sub.

The negative tank seems smaller that I would have expected.

In the pictures of the valves 1, 2, 3; they are painted black on U-995, any idea why? Are these possibly fuel lines?

The red bar handle, any idea what this does? What kind of valve it operates? It seems like a quick-opening valve of some kind.

The pair of red/blue chain-drive valves on the bulkhead, those are for the MBT 4, and another set are located on the opposite (stern) end of the control room, they open the vents for the MBT #2. That's what I think.

The exact location of the handle is hard to see on the pic. As it is located on the top, it could have been used for the fersh air conduits to the diesel engine or the internal fresh/used air pipes. Those start just start aft of the observation scope - close to the air vents for dive bunker 2 and 4.

The main ballast tank (= ballast tank #3) was located within the pressure hull beneath the control room. The two (!) negative buoyancy tanks (not two pairs) were located port and starboard in the "saddle". I do not think they were connected, and i do not know whether they "met" underneath at all.
I have some plans, but none with a section at that point.
Each negative buoyancy tank (=Untertriebszelle) had a capacity of 2,15 tons of seawater.
Will post here if i find something.

Copy from the Subsim meet thread, regarding the procedure for the neg. b. tanks:

(131. If the boat has negative buoyancy cells, the procedures are as follows: The U.-cells are being flooded when the boat is running surfaced, and in "ready to submerge" state (edit: alarmtauchklar=all men at diving positions, boat prepared for emergency dive - so .. usual condition in enemy waters), so that there is an appropriate negative buoyancy. After execution of the order "Fluten" (edit: flood the tanks!) and a perceptible tendency of falling, the cells are being blown out by order of the LI (Leitender Ingenieur).

(The best time for the blowing ballast of boats of middle size is a depth of 8-10 meters, for big boats a depth of 10-12 meters.
From experience the essential effect of the U.-cells is one of breaking through the water surface during a dive. Because the reaching of greater depths is almost entirely dependent of angle and speed (ca. 25 to 30°, 2x all ahead) it is wrong to blow them out at greater depth, because the advantage would not be in due proportion to the danger, the boat will be in. Especially wastage of air and the time of the blowing ballast increase badly.)

Anyone here has those three books from Lothar-Guenther Buchheim?
I mean those picture-books:
"Die U-Boot Fahrer"
"U-Boot Krieg"
"Zu Tode gesiegt"
Lots of pictures with explanations what can be seen on it, however not all.
If i find something about those trimming tanks..

...In the pictures of the valves 1, 2, 3; they are painted black on U-995, any idea why? Are these possibly fuel lines?

(Assumption) From the shape and location i don't think these are fuel lines. That close to the conning tower and 'shaped' like air valves these could be valves for fresh air into the different compartments of the sub(?).

Quote:

Originally Posted by Onkel Neal

...
The red bar handle, any idea what this does? What kind of valve it operates? It seems like a quick-opening valve of some kind.

(Assumption) Quick 'Entlüftung der Tauchzelle #3' (flooding of cell #3); or more likely the 'Untertriebszelle' (for quick alarm diving)?
Where is it located? - Stern / port of command room? - On the far left of the picture the vertical-scale (could be a kind of fill/pressure-indicator for a cell), could be a hint too (but when stern/port than these could be an indicator for MBT#2)...

Anyone here has those three books from Lothar-Guenther Buchheim?
I mean those picture-books:
"Die U-Boot Fahrer"
"U-Boot Krieg"
"Zu Tode gesiegt"
Lots of pictures with explanations what can be seen on it, however not all.
If i find something about those trimming tanks..

I just ran mad before my first post here since i got two Guenther Buchheim pictures-books and can't find them... but as i remember there are not that technical detailed but they would be great as source for graphical atmosphere impressions for 'Wolfpack'

Regarding the last of the 5 pictures, the two handwheels over the fore bulkhead of the control room, Buchheim writes on page 47 of his book "Die U-Boot Fahrer" that these are for the "ventilation of the two saddle tanks in the boat's center". Since there are only two exterior (saddle) tanks at the center those can be either the control wheels for the two (aft) trim tanks, or for the two (fore) negative buoyancy tanks.

What does "ventilation" mean here, Bucheim writes "Entlueftung". Is this for letting pressure air into the tank for "ventilation"? Or is it for flooding, opening the upper valves?

What i red; were the negative-tanks (Untertriebszelle? - about 2x2m²) an aid to get the boat in stronger sea under the water line (assist to flood the main-cells especially in heavy waves from stern). I am sure there were also used for alarm-diving, but they have to been blown-free with compressed air as soon the destination depth was reached... (Source: "Unterseebootbau" page 26)

...Bucheim writes "Entlueftung". Is this for letting pressure air into the tank for "ventilation"? Or is it for flooding, opening the upper valves?

"Entlüftung" means to let the air out = flooding = opening the upper valves, nice find

edit:
"ventilation of the two saddle tanks in the boat's center" => MBT #4 (Tauchbunker 4) are actualy two, port and stb. and are close to the center (slightly ahead)... i don't think that Bucheim ment a negative or trimm tank, these are the forward main-ballast tanks (?)...

Just a thought . Playing multiplayer single missions for 1 to 2 hours .
Is this turning into Neals Trimming Tanks simulator ?

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Maybe the swedes including Neal are creating the first UBoot game which can be labeled as Submarine Simulation
A submarine is nothing else than an underwater plane and good trimming is a fundemental in every flight-sim... from 'Silent Service' (C64) until SH5 we only got 'tactical' simulation of submarines, but 'Wolfpack' can also get the first submarine-simulation...

When the team thinks, get that stuff early in development into the core engine b/c it could be needed someday

I am sure there will be realism-settings later for just go and keep periscope depth, but to get a game-engine which also allows you to play the LI and try to keep periscope depth at BFT9 in north atlantic while the boss ordered to keep silent as possible
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